Synthesis of Macrocyclic Polymers Formed via Intramolecular Radical Trap-Assisted Atom Transfer Radical Coupling.
ACS Macro Lett
; 1(8): 1066-1070, 2012 Aug 21.
Article
in En
| MEDLINE
| ID: mdl-35607039
ABSTRACT
The synthesis of cyclic polystyrene (PSt) with an alkoxyamine functionality has been accomplished by intramolecular radical coupling in the presence of a nitroso radical trap. Linear α,ω-dibrominated polystyrene, produced by the atom transfer radical polymerization (ATRP) of styrene using a dibrominated initiator, was subjected to chain-end activation via the atom transfer radical coupling (ATRC) process under pseudodilute conditions in the presence of 2-methyl-2-nitrosopropane (MNP). This radical trap-assisted, intramolecular ATRC (RTA-ATRC) produced cyclic polymers in greater than 90% yields, possessing ⟨G⟩ values in the 0.8-0.9 range as determined by gel permeation chromatography (GPC). Thermal-induced opening of the cycles, made possible by the incorporated alkoxyamine, resulted in a return to the original apparent molecular weight, further supporting the formation of cyclic polymers in the RTA-ATRC reaction. Liquid chromatography-mass spectrometry (LC-MS) provided direct confirmation of the cyclic architecture and the incorporation of the nitroso group into the macrocycle. RTA-ATRC cyclizations carried out with faster rates of polymer addition into the redox active solution and/or in the presence of a much larger excess of MNP (up to a 2501 ratio of MNPC-Br chain end) still yielded cyclic polymers that contained alkoxyamine functionality.
Full text:
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Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
ACS Macro Lett
Year:
2012
Type:
Article
Affiliation country:
United States